General commercially available unsaturated nitrile is currently industrially produced, mainly, by the catalytic ammoxidation reaction of olefin, ammonia, and oxygen. On the other hand, methods which involve using an alkane such as propane or isobutane as a raw material instead of the olefin and performing gas-phase catalytic ammoxidation reaction to produce unsaturated nitrile corresponding to the raw material have received attention in recent years, and many catalysts for use in such methods have also been proposed.
For example, Patent Literature 1 describes a method for producing a catalyst for the gas-phase catalytic oxidation or gas-phase catalytic ammoxidation of propane or isobutane, wherein the catalyst contains less scattering antimony, offers a high yield of unsaturated nitrile, and exhibits a high space time yield.
Patent Literature 2 describes a production method using a silica-supported catalyst in the production of unsaturated nitrile by the gas-phase catalytic ammoxidation reaction of propane or isobutane, or unsaturated carboxylic acid by the gas-phase catalytic oxidation reaction thereof, wherein the catalyst is supported by 20 to 60% by mass of silica and satisfies a pore volume of 0.15 cm3/g or larger, and powder silica having an average primary particle size of 50 nm or smaller is used as at least a portion of a silica raw material.
Patent Literature 3 states that pores formed by silica are optimized by calcination using in combination sol and powder silica which differ in primary particle size, to thereby improve the performance of an ammoxidation catalyst and efficiently obtain a product of interest.